Finder.



I. BECKER.

FINDER. APPLICATION FILED IULYZO, ISIS.

Patanwd D00. 26, 1916.

4 MEETS-SHEET I.

fns entvf l. BECKER.

FINDER. APPLICATION FILED June, 1916.

1,210,135. Patanted 1m 26,1916

4 SHEETS-SHEET 2.

Inventor l. BECKER.

FINDER.

APPLICATION FILED IULY 20. ms.

1,210,135. Pawnted 1m 26,1916.

7 4 satin-sun a.

Inventor J. BECKER.

FINDER.

APPLICATION FILED Jun/2o, me.

Patented D00- 26, 1916.

4 SHEETS-SHEET 4.

19 7- d I 16 47! .44 w 18 4s JOSEPH BECKER, OF WASHINGTON, DISTRICT OFCOLUMBIA.

FINDER.

Specification of Letters Patent.

Patented Dec. 26, 1916.

Original application filed July 8, 1901, Serial No. 67,469. RenewedJanuary 12, 1916, Serial No. 71,809. Divided and this application filedJuly 20, 1916. Serial No. 110,310.

1 '0 all whom it may concern.-

Be it known that I, JOSEPH BECKER, acitizen of the United States,residing at Washington, in the District of Columbia, have invented newand useful Improvements in Finders, of which the following is-aspecification.

The present application, identified for convenience of reference as CaseAL, is a division of my prior application Case F, now Patent 1,195,947,issued Aug. 22, 1916.

The present specification hereinafter makes specific reference to myother related applications as follows: Case A, now Patent 1,178,474,issued April 4, 1916; Case B, now Patent 1,178,475, issued April 4,1916; Case C, now Patent 1,178,476, issued April 4, 1916; Case D, nowPatent 1,190,623, issued July 11, 1916; Case F, specified in theimmediately preceding paragraph as the parent application of the presentdivision Case AL; Case J, Serial No. 246,169, filed February 17, 1905;Case 1V, now Patent 1,195,948, issued Aug. 22, 1916; Case Ah, Serial No.87,977, filed March 31, 1916, as a division of my said Case C.

My present invention relates to camera finders of the type comprising afinder lens that forms a small size image of the camera field, and theinvention consists in so constructing the said finder lens that it shallitself comprise a removable lens element which is adapted to be removed,at will, to permit of seeing the central part of the finder field onanenlarged scale; such novel result being useful and desirable wheneverthe object being photographed, or details in such object, are too smallto be easily distinguished in the normal finder image that is producedwhen the said removable lens element is in operative position.

- A finder comprising a removable lens element whose removal has thesame effect of increasing the scale of the finder image is already shownin Figure 11 of my said case C; also in Fig. 3 of my said Case Ah; andagain in my said Case J; but the removable lens element of these threeother applications is an eccentric lens and is adapted to cooperate witha corresponding removable lens -element of the camera objective;whereas, the present removable lens element is centric and is usefuleven when the camera objective does not contain any removable lenselement.

My present invention is specially useful where the finder is a combinedfocus and field finder such as shown in my said Cases B, C, D and F; butthe accompanying drawings show it only as applied, in two differentforms, to the specific form of focus and field finder seen in my saidCase F.

Fig. 1 is a horizontal section similar to Fig. 20f my said Case F, butshowing the removable lens element in removed position or position ofnon-use, and as having a focal length that is equal to that of theimmovable lens element. Fig. 2 is a similar View of the same camera butshowing the removable lens element in position of use to coiiperate withthe immovable lens element as a compound finder lens having an angularfield Me"N substantially equal to that of the camera objective. Figs. 3and 4 are views corresponding, respectively, to Figs. 1 and 2, butshowing a modified form of finder Whose immovable lens element has afocal length that is infinitely long.

The camera comprises a .box 1 with hinged cover 2, which is shown heldopen in horizontal position to serve as camera bed. Parts 4; 5, c, 12,13, 14, 16, 17, 1s, 19, 21, 23, 24, 34 and 35 are all fully described inmy said Case F, and it need only be recalled that the part 34, 35,pivoted at 24, carries the pivoted mirror of the focuserl The fixedmirror of the focuser is in the shape of a reflecting prism 36, cementedat the middle of a divergent lens 37, which is firmly held by clamfingers (seen at 38 in Fig. 1 of my said ase F) in a chamber formed by,sheet metal partitions 39 and 40, which are fixed within the box-likeframe 16. The bottom 40 of this chamber is perforated with an openingcorresponding to the camera plate and as the camera shown is square,with reversible back to take plates either way, the said opening has theoutline formed by superposing crossed plates. Partition 40 is continuedto the left, as at 41, to form a slideway for a second divergent lens42, which is. mounted ina rectangular framing or carriage 43, and thiscarriage 43 is adapted to fit the slideway nicely so it will remaintherein wherever it may have been set by actin with a finger, on theprojecting'lug 44. en lens 42 is in the position-shown in Fig. 1, lens37 is alone in use,.1and the Kid finder field, for the eye at E, has therelatively small angular value AeB; but, when lens 42 is shoved to theright as shown in Fig. 2, the two lenses operate together as one lens ofabout twice the strength of lens 37, and the finder field, for the sameeye at E, then has the angular value Md'll, which is the same as that ofthe camera field. The reason for not using this one strong lens in allcases, even in a plain field finder without focusing mirror, is thatvery often it is more desirable to see details of the finder image as inportraiture, when the operator wishes to wait for the expression, and inthis case the central part of the field is usually alone important. Themain object being centered on the plate, what the limits of the fieldmay be is generally quite secondary. d'ith the double lens the operatorcan see what the limits are, then, when about to expose, he uses thesingle lens for focusing and for centering.

The focal lengths of lenses 37 and A2, shown equal in Figs. 1 and 2, mayhave any other desired relative value, provided only the two lensesacting together have the proper resultant focal strength to show acorrect field. lhus in Figs. 3 and A the nonmovable lens is a piece ofplate glass 37, whose focal length is infinitely long. The movable lens42 must accordingly be of sufficiently short focal length to show afinder field having an angular value l /lc ld, Fig. 4, equal to Me N ofFig. 2, and to the camera field.

lln Fig. 1 the extreme finder rays are AAFJ and BBE; and the incidentalparts AA, BB of these extreme rays, produced, meet in c, which is thevirtual image as well as the virtual position of the observers eye F).In Fig. 2 the extreme finder rays proceeding from Ml and Nfirst convergein c; then, after having traversed lens 37, they converge in e; finally,after traversing the lens 4-2, they converge in the observers eye at F.Points 6 and c, Fig. 2, are therefore the successive virtual images aswell as the successive virtual positions of the observers eye In Fig. 3the plate glass 87 being a lens of infinite focal length forms the imageof E in very nearly the same point E; and in Fig. A the conjugate of Eis ate The conjugate points 0 in Fig. 1, e" in Fig. 2, and e' in Fig. 4.are not purely theoretical points, for they represent the images of eyeE as they would be seen by a person standing in the samera field.

l lo'rn 1.-Fig. 1 of the present Case All: is based on Fig. 2 of my saidCase F as such Fig. 2 appeared when originally filed. See the threeapproximately half size blue prints made July 17, 1901, and on file, ofrecord in said Case F, si. ce August 25, 1902. The present 2 of i saidis the re sult of amendments noted page 4: of the paper dated February15, 1910 in the Patent Office record of such Case F.

NOTE 2.-Fig. 3 of the present Case AL is substantially identical withthe original and now canceled Fig. 3 of my said Case F.

N o'rn 3.Claims 1, 2 and 3 made below are an exact copy of the claimspresented August 28, 1902, in my said parent application, Case F, asclaims 12, 13, and 1%, respectively; and claims A and 5 are the same asclaims 1 and 2 but limited to a removable lens that is centric.

No'rn A- Where the camera objective is compound and separable todetermine two different focal lengths for the camera, the finder lensesshould preferably be proportioned to correspond in accordance witi theprinciples explained in Fig. 11 of my said Case C, or Fig. 3 of my saidCase Ah, and in my said Case J.

Norm 5.-'lhe mirrors of my focuser, as explained in my said Case C, page3, lines 7% to 80, also in my said Case A, page 19, lines 15 to 25, areused to sight and determine what shall be the central point of thepicture and to this extent they alone constitute a. camera finder. Mypresent inyention therefore determines a type of finder that isintermediate between the purely centering finder and the complete fieldfinder.

No'rn 6.-lhe removable eccentric lens seen in Fig. 11 of my said Case C(or 8 of my said Case Ah) cannot be removed withol it enlarging thescale of the finder image, but such enlargement in scale is purelyaccidental as the prime object, in my said Case C, is to secure a changein the extent of the finder field, and this change is also accompaniedby a change in the height of the observer s eye. llf the lens Z, in Fig.11 of my said Case C, were removable for the sole purpose of producing achange in the scale of the finder image, the single lens long focusfinder Z would have to be used in combination with the compound lensshort focus camera-objective 81, 82, and this is not practicablebecause, the central finder ray would drop so as to proceed into thecamera box instead of over it. In applying my present invention,therefore, to the camera of my said Case C, the

. finder must be designed so that the removable finder element l shallbe centric or at least not sufficiently eccentric to be inoperative forthe purpose set forth in the present application Case AL.

What ll claim as my invention and desire to secure by Letters Patent is:

1. photographic finder comprising a minus lens of finite focus adaptedto be removed out of the path of the rays that pass through the finder,in order to change tne scale the finder ge, or ratio of finder of meansfor changing the scale of the finder image, that is the ratio of alinear dimension in the finder image to the same dimension in theoriginal object, substantially as and for the purpose set forth.

A photographic finder comprising a centric minus lens of finite focusadapted to be removed out of the path of the rays that pass through thefinder, in order to change the scale of the finder image, or ratio of alinear dimension in the finder image to the same dimension in theobject.

5. A photographic finder comprising a centric finite focus lens adaptedto be removed to change the scale of the finder image, or ratio of alinear dimension in the finder image to the same dimension in theoriginal object.

In testimony whereof, I have signed my name to this specification.

JOSEPH BECKER.

